Save flash space

* No weak link for modules. It only impacts _os and _time and is
  already disabled for non-full builds.
* Turn off PA00 and PA01 because they are the crystal on the Metro
  M0 Express.
* Change ejected default to false to move it to BSS. It is set on
  USB connection anyway.
* Set sinc_filter to const. Doesn't help flash but keeps it out of
  RAM.

Author: tannewt

ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h

@@ -33,6 +33,10 @@
 #define DEFAULT_UART_BUS_RX (&pin_PA11)
 #define DEFAULT_UART_BUS_TX (&pin_PA10)
 
+// These pins are connected to the external crystal.
+#define IGNORE_PIN_PA00     1
+#define IGNORE_PIN_PA01     1
+
 // USB is always used internally so skip the pin objects for it.
 #define IGNORE_PIN_PA24     1
 #define IGNORE_PIN_PA25     1

ports/atmel-samd/common-hal/audiobusio/PDMIn.c

@@ -326,7 +326,7 @@ static void setup_dma(audiobusio_pdmin_obj_t* self, uint32_t length,
 // higher sample rate than specified.  Then after the audio is
 // recorded, a more expensive filter non-real-time filter could be
 // used to down-sample and low-pass.
-uint16_t sinc_filter [OVERSAMPLING] = {
+const uint16_t sinc_filter [OVERSAMPLING] = {
     0, 2, 9, 21, 39, 63, 94, 132,
     179, 236, 302, 379, 467, 565, 674, 792,
     920, 1055, 1196, 1341, 1487, 1633, 1776, 1913,

py/circuitpy_mpconfig.h

@@ -186,7 +186,7 @@ typedef long mp_off_t;
 #define MICROPY_CPYTHON_COMPAT                (CIRCUITPY_FULL_BUILD)
 #define MICROPY_PY_BUILTINS_POW3              (CIRCUITPY_FULL_BUILD)
 #define MICROPY_COMP_FSTRING_LITERAL          (MICROPY_CPYTHON_COMPAT)
-#define MICROPY_MODULE_WEAK_LINKS             (CIRCUITPY_FULL_BUILD)
+#define MICROPY_MODULE_WEAK_LINKS             (0)
 #define MICROPY_PY_ALL_SPECIAL_METHODS        (CIRCUITPY_FULL_BUILD)
 #define MICROPY_PY_BUILTINS_COMPLEX           (CIRCUITPY_FULL_BUILD)
 #define MICROPY_PY_BUILTINS_FROZENSET         (CIRCUITPY_FULL_BUILD)

supervisor/shared/usb/usb_msc_flash.c

@@ -39,7 +39,7 @@
 
 #define MSC_FLASH_BLOCK_SIZE    512
 
-static bool ejected[1] = {true};
+static bool ejected[1] = {false};
 
 void usb_msc_mount(void) {
     // Reset the ejection tracking every time we're plugged into USB. This allows for us to battery